OT: Backing up machine to machine, cvsup vs. rsync vs... ?

[Communications Machine]

Hey all,

Looking for a (cheap but effective) solution to nightly backup or
synchronize about 100-200gigs of data. Figure this might be a tad bit
off-topic, but sent to the general questions list hoping to find anyone out
there doing something similar. I was hoping to do something along the lines
of cvsup or rsync, so-as to only have to sync changes daily.

Here's a better picture of the scenario:
~~~~~~~~~~~~~~~~~~~~~~~~~~
File Server 1 has (roughly) 750GB Storage on RAID 5 Array, runs as a PDC
using combination of Samba, OpenLDAP and some in-house utilities. This
machine is very fast by comparasin to all of our other machines (dual AMD
Opteron 244, 2GB RAM, running 5.3-RELEASE/amd64), and runs under minimal
load/stress.

Server two runs as an incoming filter for email
(spamassassin/mimedefang/custom stuff using milter interface), and as a
proxy server for network users during the day (running squid). This machine
is considerably slower (AMD 350Mhz K62, 768Mb RAM, ATA133 disks running
4.9-RELEASE/i386), but should be adequate for the job. This machine has two
80GB disks which we'd like to use to sync data to.

Ideally, we would like to backup certain directories nightly, so as to have
a mirror of the important files (100-200GB or so) on the second server in
the event that the first ever goes down, (essentially avoiding a tape-backup
solution we cannot afford).

The two machines will be connected with a dedicated ethernet link (cross
cable) driectly from to each other at 100Mbps.

How do I reliably synchronize the data in selected directories from one
machine to the other on a nightly basis? Any
ideas/suggestions/comments/questions will be greatly appreciated.

--
Thank-you
Nathan Vidican
itstaff at wmptl.com